Observations of the 12/13th November 2004 Rain Event – A Review
During my recent stay in Tobago I was quite taken aback by the size of the huge landslides and tell tale signs where huge volumes of water cascaded down the slopes of Tobago last November.
The visible evidence of this is not that apparent and you have to trek around some very rural areas to see the real signs of the power of this major weather event … or you can peep over the sides of the bridges and boundaries in the area of Speyside and Delaford to see how much rainforest vegetation actually dislodged and rushed down into the valleys.
If you are going on holiday, don’t worry … you will hardly notice anything … but if you do happen to see the signs, please spare a thought for the 4 people that died during this event.
As was reported at the time, the areas of Delaford, Speyside and Charlottesville took some of the heaviest damage and I have to say that it seems quite miraculous that only 4 deaths occurred when you realise how heavily populated these areas are.
Many of the dwellings in these areas found themselves in the direct path of the cascades of water rushing down the hillsides.
Even larger landslides were evident along the north coast through the Castara and Englishman’s areas and right up to Bloody Bay and L’Ansi Fourmi, however these are more remote areas where fewer people dwell in houses on the steep slopes.
The raw power of this weather event was pure rainfall and 18 inches or more of it literally tipped out of the skies continuously for about 16 hours … rainfall of this volume has never fallen over Tobago in recorded history in such a short space of time.
The sheer volume of water was sufficient to undermine, uproot and carry some of the largest trees high up in the rainforest miles down the rivers and hillsides, crashing through Bamboo Trees and other smaller Rainforest vegetation and many such trees can be seen intact in places, lying across rivers or wedged under a bridge.
Some bridges have cracks in their structure, not to mention the concrete structures that border the roads in some places where tonnes of forest debris simply plunged down the steep hillsides as the land underneath it simply gave way.
Only in the remotest areas, such as the rainforest surrounding Hermitage Bay (near Charlottesville) could the evidence really give me some impression of the power of this weather event and a sense of the fear that must have been going through the minds of those that experienced it.
So what happened?
I had only started the weather forecasts on Liquid Sunshine 3 weeks earlier and my weekly weather update for the 6th November showed my concern about the disturbed weather patterns developing around the southern Caribbean.
But huge storm cells such as the one that affected Tobago on this occasion are very difficult to predict … you know they will form in an area but you don’t know exactly where the rain will fall and then you do not know where they will go and as quickly as they form they can dissipate and disappear very quickly … as the following excerpts from my weather updates and weekly report show …
Excerpt from Weekly Weather 06.11.2004
How does this Rain Form?
The exact location of the rainfall is difficult to predict.
Tobago, being around 10 degrees north of the equator, is always very close to or within what is known as the Inter-Tropical Convergence Zone which marks the area where the trade winds from the south and the north converge.
The convergence of these very warm and moist winds create ‘cells’ or ‘hot towers’ of cloud that bubble up very quickly and produce the downpours that Tobago has been receiving.
The Tropical Cells are known as ‘Hadley Cells’ and are the most vigorous types of thunderstorm formation on earth … they can form very quickly into clusters of storms and, occasionally, a cluster may get itself really organised under the right conditions and start to circulate … this is how Tropical Storms and Hurricanes can form.
Next Week
We need to look to the east where clusters of storm activity are developing as they cross the Atlantic Ocean from Africa though not all of these will reach Tobago as some dissipate or are sheared back by the dominant high pressure in the northern Caribbean.
We also need to look to the south and the mainland of South America for the most likely source of rain. This is where most of the rain has come from over the last 2 weeks and I expect this trend to continue.
Mid-week, it looks like low pressure will form across most of the Caribbean as the high slips away to the east. I am watching this development as this could mean widespread rainfall across the Caribbean.
As I had predicted, the weather really got it’s act together midweek.
The following series of weather updates and warnings that I posted will give us an impression of how the disturbed weather conditions developed …
WEATHER WARNING 10th November 2004. 1430 GMT - UPDATE
RISK OF VERY HEAVY RAIN
Grenada and the chain of islands to the north as far as Dominica are now being affected by this pulse of intense rainfall.
There are some indications that the intensity of this main area of rainfall is weakening slightly in places and it’s progress has slowed down slightly, however further areas of intense rainfall are brewing up very quickly and a very intense cell is developing just behind this area to the north-west and is following the same track.
The risk is increasing for Tobago as this area of rainfall moves east south-east,
Then, 7 hours later …
WEATHER WARNING 10th November 2004. 2100 GMT - UPDATE
RISK OF VERY HEAVY RAIN FOR THE NEXT 24 – 48 HOURS
Tobago has been extremely lucky so far as the first pulse of rain dissipated over Tobago giving some sharp showers and Trinidad got the main deluge.
In fact, the south western part of Trinidad is being affected by another developing cell and this is giving very intense rainfall.
Further bands of thunderstorms and pulses of heavy rainfall are lining up to the north-west.
These storm cells can weaken as quickly as they can develop and it is very difficult to predict exactly when Tobago could be affected.
The south eastern Caribbean is currently peppered with this stormy activity.
There is more to come over the next 24 to 48 hours before this low pressure system to the north moves away into the Atlantic.
Lets hope Tobago stays lucky …
24 hours later …
WEATHER WARNING 11th November 2004. 2145 GMT - UPDATE
STILL THE RISK OF VERY HEAVY RAIN
The weather is currently very disturbed and yet Tobago has come so close and escaped … i.e.; the storm activity has been very localised.
At the time of writing, the rainfall is coming from the west and a small cell has already just veered to the south of Tobago.
Again, there is plenty developing from behind and there is still the risk that Tobago could catch one of these cells …
And then it came …
WEATHER UPDATE 12th November 2004. 1930 GMT - UPDATE
REDUCING RISK OF VERY HEAVY RAIN
Tobago has been affected by intense and continuous rainfall for over 14 hours.
This main area of rain is expected to cease in the next 1 – 2 hours but there are smaller cells of rainfall following behind that may affect Tobago and produce shorter periods of heavy rain.
Summing Up
Earlier, in September, Hurricane Ivan gave Tobago a licking although this was, in hindsight, a lucky escape. The hurricane was very powerful and would have devastated Tobago has it tracked 20 miles or more further to the south.
The devastation in Grenada is an indication of the damage that could have been.
The only visible signs of the Hurricane in Tobago are evident from a few missing palm tree heads, some fallen trees and the jetty in Batteaux Bay that was damaged and is due to be repaired.
The November rainfall event was the weather event of the year by some distance … probably one of the most significant events of the last century although some may argue that the damage from Hurricane Flora in 1963 was worse with the loss of countless trees.
Apart from the visible damage that I outlined earlier in this post, the amount of ecological damage is difficult to measure.
Hurricane damage is generally restricted to the land although some coral damage can occur where the reefs are not sheltered from the battering waves.
In this case it was rain and this can seep into every single pore. It was so heavy that it would have diluted the salt in the sea for days.
Even 6 months later, the sea (at high tide) is washing away the remnants of landslides that have reached the coasts and creating brown slicks of mud that are being washed out to sea and over the coral reefs around the coasts.
Much of the coral is struggling under the sediment that is falling on it and I have seen evidence of this in Heavenly Bay, Castara and in Charlottesville along the main beach.
I have also heard that the fish stocks have reduced as the local food the fish rely on has reduced.
There is still some slippage on the hillsides in northern and eastern areas of Tobago and I would be surprised if any further heavy rain in the forthcoming wet season does not cause further slides.
The recovery from Hurricane Ivan was swift but the effects of the November 2004 rain event are still there. It may be some time before we know the full extent of the ecological damage.
This was all down to Mother Nature … lets hope that Mother Nature will be kinder to Tobago in the next wet season and allow the corals to breath and the vegetation to knit the loose soil back together … it looks a little delicate in some places.
Regards
